I've spent a few hours looking at SketchUp, and maybe 15 years on DesignWorkshop... hardly what you could call an even balance. Anyway, here's what I've figured out so far...

Similarities

At first impression, the similarities are substantial. Both DesignWorkshop® Professional and SketchUp are 3D design tools aimed primarily at architects. Both provide more live and dynamic 3D interaction, within simpler user interfaces, than is available from traditional 3D CAD software.

This is pretty cool. Since the fading of ModelShop and UpFront years ago, and ConceptCAD more recently, DesignWorkshop has been pretty much alone in the category of 3D conceptual design software for architecture. You'd think that would be good (and honestly, we weren't complaining) but the big firms and analysts hardly notice a category with just one small company serving it, and one using pure word-of-mouth marketing at that.

We welcome principled competition, and think that a healthy market will provide architects with a choice of alternative tools. Most architects are not using 3D digital tools for conceptual and schematic design yet at all. Getting the profession accustomed to the basic availability of 3D sketching tools has been our biggest hurdle for the last nine years. (SketchUp might be already helping in this area, with DesignWorkshop sales continuing at historically record levels.)

Of course, we have some inherent resistance to welcoming any software that simply copies tools that we have innovated, and we really don't welcome empty marketing hype like SketchUp's apparent claim to be 'the AEC industry standard (whatever)'. If we can focus on real similarities and differences, I think we're doing a better service to our customers for the long run.

Differences

As much as there is overlap in the intended focus of SketchUp and DesignWorkshop Professional, there are fundamental differences, in user interface, in underlying technology, and in scope of application.

Simplicity

Both tools claim to provide simple, design-oriented 3D modeling. But how simple is simple?

The DesignWorkshop tools are presented in 31 application-specific icons. SketchUp appears to have about 37 application-specific icons, plus about 13 more generic Windows toolbar icons. Those 50 or so total icons do include some options that DesignWorkshop leaves in the menus, like printing. Even so, neither presents a really big complex traditional-CAD type interface.

Efficiency

More importantly, what lies behind the icons? Or in other words, how does one work in the program? We think modeling efficiency is absolutely critical in a 3D design tool. Simplicity and efficiency together are essential for design tools that let you forget about them while you're designing.

Taking a close look at both programs, I think you'll find that modeling operations are typically quicker and simpler in DesignWorkshop, providing significantly more modeling efficiency.

For instance, to cut a window into a selected wall in DesignWorkshop takes just one gesture  drag out the window rectangle on the wall. Cutting a hole in the front surface of the wall, extending the window side surfaces through the wall cavity, and cutting the hole in the back wall surface are all handled automatically, in real time, as part of the one opening gesture. To do the same thing in SketchUp requires several steps.

This simplicity/efficiency difference is built into the basic structure of the two user interfaces.

During years of grappling with the principles of graphical user interfaces, I came up with a simple rule of thumb. If you need to give a "Move" command just to drag objects around in the drawing or modeling environment, you don't have a truly simple, powerful, direct-manipulation user interface. The original standard setters in this area  MacDraw, ClarisCAD, PowerCADD, MiniCAD  didn't/don't require a Move command.

DesignWorkshop takes that philosophy to heart. In the default Arrow Tool of DesignWorkshop, you can move objects, resize objects, reshape objects, and even extrude objects. All of these basic modeling operations, which are critical to massaging and evolving the elements of a design in process, just 'happen', simply by pushing and pulling on different parts of selected objects. Essentially, no tools are needed  these manipulations are just built into the DesignWorkshop 3D crosshair and the DesignWorkshop working environment.

In contrast, SketchUp requires separate tools for moving, scaling, and their reshape operations of push-pull and offset. This slows down the modeling process, as you have to go back to the tool palette over and over again even while doing the most basic model adjustments. More important than the speed effect, however, is the cognitive effect. Every time your mind has to trigger the hand and eye moves to switch to a different new tool to work with, it has to snap out of that essential designer's conceptual mind-meld with the architectural space being created.

In user interface lingo, SketchUp is much more "modal" than DesignWorkshop. The SketchUp user has to put the software into the correct state, by selecting the specific right tool, in order to perform any task.

These are nitty-gritty issues, that architectural software users shouldn't usually have to spend time thinking about. But this is also one area where the rubber hits the road in digital design tools. It's an area worthy of attention from professionals who take their tool choices seriously.

Technology

There's an even more basic aspect to the design power of simple modeling in DesignWorkshop, as compared to SketchUp. DesignWorkshop is fundamentally a feature-based solid modeler, while SketchUp is fundamentally a surface modeler  something of a technological throwback.

At the user interface level, feature-based solids are part of what lets DesignWorkshop provide all that built-in no-tools modeling power. Feature-based solids are created inside the software with extra levels of connectivity information, which is used in DW so that dragging on a face automatically does one thing, while dragging on a corner handle does another, and dragging on a mid-edge handle does another.

DesignWorkshop knows the difference between a 2D construction line and a 3D solid, so when the user drags sideways on a corner handle of a construction line, it has the intelligence to seamlessly extrude the line into a solid, and then automatically keep scaling the new solid as the user keeps dragging.

And this extra feature-based solid object information is what powers the Object Info box in DesignWorkshop, for instant non-modal numerical editing of object size and position.

SketchUp provides some nifty enhancements to the classic surface modeling operations, such as connecting faces so at times they move and stretch together. But with the surface-based approach, SketchUp is playing catch up to what's almost automatic in the direct manipulation of solids.

Paradigm

There are several other important implications of the surfaces-versus-solids technology gap which I'll have to get back to later. But there's one more basic thing I want to touch on.

The modeling paradigm behind SketchUp seems to be basically drawing, pencil and ruler on paper, moved cleverly into a 3D workspace. Objects are created by drawing lines, which close up to form surfaces when they make closed loops. A building is assembled from these surfaces, drawn up line by line.

The benefit of the drawing approach may be that traditional architects are comfortable with drawing, and with lines. This may provide some easy initial popularity for SketchUp (though their sales seem to be pretty typical of new products in this market niche), and it fits well with their 'drawing on napkins' marketing theme. But in the long run, I think it sells short the potential of digital 3D design.

In contrast, the modeling paradigm behind DesignWorkshop is basically modeling. A building is built up out of solid objects, masses, walls, columns, beams (using magic elastic digital cardboard/clay that always keeps its sides smooth and flat, and corners neat and square (when wanted)). The general metaphor not drawing a building in 3D, but rather, constructing a building in 3D.

DesignWorkshop is based on the philosophy that architecture is not about drawings  not even cool 3D drawings. Architecture is about buildings, and buildings are made from objects, solid objects with palpable dimensions, not just from lines and surfaces.

Tools that enable the designer to build in 3D, quickly and fluently with objects, with a minimum of distracting modes and functions, and with a maximum of user-controlled flexibility, we think will ultimately allow architects to get closer to their art and craft.

It's a big task for just a few million lines of software. But that's our vision  not better sketches, but better buildings.